Multilayer printed circuit board

ABSTRACT

The objective of present invention is to provide an electroplating solution capable of forming the upper face of a via-hole and the upper face of a conductor circuit in the same layer in approximately the same plane at the time of manufacturing a multilayer printed circuit board. The electroplating solution of the present invention is characterized by containing 50 to 300 g/L of copper sulfate, 30 to 200 g/L of sulfuric acid, 25 to 90 mg/L of chlorine ion, and 1 to 1000 mg/L of an additive comprising at least a leveling agent and a brightener.

CROSS REFERENCE TO RELATED APPLICATION

This is a divisional application of U.S. application Ser. No.10/864,400, filed Jun. 10, 2004, now U.S. Pat. No. 7,446,263, which is adivisional of U.S. application Ser. No. 10/048,852, filed Apr. 11, 2002,now U.S. Pat. No. 7,514,637 which claims priority of Japanese PatentApplication 11/224143, filed Aug. 6, 1999, Japanese Patent Application2000/156877, filed May 26, 2000, Japanese Patent Application2000/156878, filed May 26, 2000, Japanese Patent Application2000/194619, filed Jun. 28, 2000, and Japanese Patent Application2000/194620, filed Jun. 28, 2000. The entire disclosures of the priorapplications are considered part of the disclosure of this divisionalapplication and are hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates to an electroplating solution to beemployed for manufacturing a multilayer printed circuit board, a methodfor manufacturing a multilayer printed circuit board using theelectroplating solution, and a multilayer printed circuit board.

BACKGROUND ART

A multilayer printed circuit board so-called a multilayer-built-upwiring substrate is manufactured by a semi-additive method and the likeand produced by building up a conductor circuit of copper and the likeand an interlaminar resin insulating layer on a resin substrate,so-called a core, of approximately 0.5 to 1.5 mm thickness andreinforced with glass cloths and the like serially in alternate fashionand in repetition. The interconnection of the conductor circuits throughthe interlaminar resin insulating layer of the multilayer printedcircuit board is achieved by a via-hole. Conventionally, themultilayer-built-up printed circuit board is produced according to amethod disclosed in, for example, JP H09-130050 A and the like. That is,at first a through hole is formed in a copper-laminated laminatesubstrate bearing a copper foil and successively subjected to anelectroless copper plating to complete the plated-through hole.Continuously, the surface of the substrate is etched in a conductorpattern to form a conductor circuit, and on the surface of the conductorcircuit, a roughened surface is formed by electroless plating, etchingand the like. After a resin insulating layer is then formed on theconductor circuit having the roughened surface, the resultant resinlayer is subjected to exposure and development treatment to form anopening part for a via-hole and then the resin layer is subjected to UVcuring and main curing treatment to form an interlaminar resininsulating layer.

Further, after the interlaminar resin insulating layer is subjected toroughening treatment by an acid, an oxidizing agent and the like, a thinmetal layer is formed thereon and a plating resist is formed on themetal layer, and then thickened by electroplating. After the platingresist is separated, etching is carried out to form a conductor circuitconnected with a conductor circuit of the lower layer through thevia-hole.

After these processes are repeated, a solder resist layer for protectingthe conductor circuit is formed finally and then such part where anopening part is exposed to connect an electronic part such as an IC chipand a mother board is plated and successively a solder bump is formed byprinting a solder paste to complete the manufacture of amultilayer-built-up printed circuit board.

In manufacture of such a multilayer-built-up printed circuit board, inthe case that a conductor circuit connected with a conductor circuit ofa lower layer through a via-hole by carrying out electroless plating andelectroplating, the opening part for a via-hole is not completely filledwith a metal and as being shown in FIG. 25, a recessed part is formed inthe peripheral part of the via-hole. Incidentally, FIG. 25 is across-section figure illustrating the cross-section of a via-hole of aconventional multilayer printed circuit board.

SUMMARY OF THE INVENTION

As described above, in a multilayer-built-up printed circuit board, theupper face of the conductor circuit, especially the peripheral part of avia-hole, is not flat, so that in the case of forming an interlaminarresin insulating layer on the upper face of conductor circuit, theinterlaminar resin insulating layer is sometimes waved to result inseparation of the interlaminar resin insulating layer and crackformation and disconnection of the conductor circuit to be formed on theupper layer of the interlaminar resin insulating layer as well.

Further, a stack via structure (a structure in which a via-hole isformed immediate above another via-hole, reference to FIG. 1) isrequired as a structure of a multilayer-built-up printed circuit boardto shorten the wiring distance in order to provide a printed circuitboard with high speed performance and fine structure. However, since anopening part for a via-hole in a multilayer-built-up printed circuitboard manufactured by a conventional method as described above is notperfectly filled with a metal, it becomes difficult to form the stackvia structure.

The inventors of the present invention have found based on the resultsof the enthusiastic investigation of the above described objects that anopening part for a via-hole can perfectly be filled with a metal byusing an electroplating solution containing a specified amount of anadditive composed of a specified levelling agent and a brightener andthat the upper face of a via-hole and the upper face of a conductorcircuit in the same layer can be kept approximately in the same planeand have achieved the present invention comprising the following subjectmatter.

That is, an electroplating solution of the present invention is anelectroplating solution to be employed for manufacturing a multilayerprinted circuit board composed of a substrate bearing a conductorcircuit and, as serially layered thereon, a resin insulating layer and aconductor circuit in an alternate fashion and in repetition,characterized by containing 50 to 300 g/L of copper sulfate, 30 to 200g/L of sulfuric acid, 25 to 90 mg/L of chlorine ion, and 1 to 1000 mg/Lof an additive comprising at least a levelling agent and a brightener.

As the foregoing levelling agent, at least one substance selected fromthe group consisting of polyethylene, its derivatives, gelatin, and itsderivatives is preferable to be used and as the foregoing brightener, atleast one compound selected from the group consisting of sulfur oxide,compounds related to sulfur oxide, hydrogen sulfide, compounds relatedto hydrogen sulfide, and other sulfur compounds is preferable to beused.

A first method for manufacturing a multilayer printed circuit board ofthe present invention is characterized by containing at least thefollowing processes (a) to (e):

-   (a) a process of forming a resin insulating layer having an opening    part for a via-hole by exposure and development treatment or laser    treatment;-   (b) a process of forming a metal layer comprising at least one    element selected from the group consisting of Cu, Ni, P, Pd, Co and    W on the surface of the resin insulating layer and the opening part    for a via-hole;-   (c) a process of forming a plating resist on the foregoing metal    layer;-   (d) a process of forming an electroplating film on a part un-coated    with the foregoing plating resist using an electroplating solution    of the present invention; and-   (e) a process of forming a conductor circuit by etching the metal    layer existing under the foregoing plating resist after the    foregoing plating resist is separated.

Further, a second method for manufacturing a multilayer printed circuitboard of the present invention comprises at least the followingprocesses (a) to (d):

-   (a) a process of forming a resin insulating layer having an opening    part for a via-hole by exposure and development treatment or laser    treatment;-   (b) a process of forming a metal layer comprising at least one    element selected from the group consisting of Cu, Ni, P, Pd, Co and    W on the surface of the resin insulating layer and the opening part    for a via-hole;-   (c) a process of forming an electroplating film on the metal layer    using an electroplating solution of the present invention; and-   (d) a process of forming a conductor circuit by etching after an    etching resist is formed on the foregoing electroplating film.

In the foregoing first and second method for manufacturing a multilayerprinted circuit board of the present invention, the metal layer ispreferable to be formed by sputtering, plating, or sputtering andplating in combination in the process (b).

Further, the foregoing interlaminar resin insulating layer is preferablyat least one resin selected from the group consisting of a fluoro resin,a polyolefin type resin, and a polyphenylene type resin or a resincomplex containing a thermoplastic resin and thermosetting resin.

Further, in the foregoing first and second method for manufacturing amultilayer printed circuit board of the present invention, at least onesubstance selected from the group consisting of polyethylene, itsderivatives, gelatin, and its derivatives is preferable to be used asthe foregoing levelling agent for the electroplating solution and atleast one compound selected from the group consisting of sulfur oxide,compounds related to sulfur oxide, hydrogen sulfide, compounds relatedto hydrogen sulfide, and other sulfur compounds is preferable to be usedas the foregoing brightener for the electroplating solution.

A multilayer printed circuit board of the present invention is amultilayer printed circuit board comprising a substrate bearing aconductor circuit and, as serially layered thereon, a resin insulatinglayer and a conductor circuit in an alternate fashion and in repetition,wherein the conductor circuits neighboring in up and down direction areconnected through a via-hole, characterized in that the foregoingvia-hole is filled with a metal, that the upper face of a via-hole andthe upper face of a conductor circuit in the same layer are keptapproximately in the same plane and that the distance from the bottomface to the upper face of the foregoing via-hole is about 2 to 7 timesas long as the thickness of the foregoing conductor circuit.

In the foregoing multilayer printed circuit board, the foregoing resininsulating layer is preferable to have a dielectric constant of 3.0 orlower at 1 GHz.

Further, the foregoing multilayer printed circuit board is preferablymanufactured by the foregoing first or second method for manufacturing amultilayer printed circuit board of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The patent or application file contains one drawing executed in color.Copies of this patent or patent application with the color drawing willbe provided by the Office upon request and payment of the necessary fee.

FIG. 1 is a cross-section figure showing one cross-section of amultilayer printed circuit board of the present invention.

FIGS. 2( a) to (d) are cross-section figures showing a part of processesof manufacturing a multilayer printed circuit board of the presentinvention.

FIGS. 3( a) to (d) are cross-section figures showing a part of processesof manufacturing a multilayer printed circuit board of the presentinvention.

FIGS. 4( a) to (d) are cross-section figures showing a part of processesof manufacturing a multilayer printed circuit board of the presentinvention.

FIGS. 5( a) to (c) are cross-section figures showing a part of processesof manufacturing a multilayer printed circuit board of the presentinvention.

FIGS. 6( a) to (c) are cross-section figures showing a part of processesof manufacturing a multilayer printed circuit board of the presentinvention.

FIG. 7( a) is a cross-section figure showing a part of processes ofmanufacturing a multilayer printed circuit board of the presentinvention.

FIGS. 8( a) to (d) are cross-section figures showing a part of processesof manufacturing a multilayer printed circuit board of the presentinvention.

FIGS. 9( a) to (d) are cross-section figures showing a part of processesof manufacturing a multilayer printed circuit board of the presentinvention.

FIGS. 10( a) to (c) are cross-section figures showing a part ofprocesses of manufacturing a multilayer printed circuit board of thepresent invention.

FIGS. 11( a) to (c) are cross-section figures showing a part ofprocesses of manufacturing a multilayer printed circuit board of thepresent invention.

FIGS. 12( a) to (c) are cross-section figures showing a part ofprocesses of manufacturing a multilayer printed circuit board of thepresent invention.

FIGS. 13( a) to (b) are cross-section figures showing a part ofprocesses of manufacturing a multilayer printed circuit board of thepresent invention.

FIGS. 14( a) to (d) are cross-section figures showing a part ofprocesses of manufacturing a multilayer printed circuit board of thepresent invention.

FIGS. 15( a) to (d) are cross-section figures showing a part ofprocesses of manufacturing a multilayer printed circuit board of thepresent invention.

FIGS. 16( a) to (d) are cross-section figures showing a part ofprocesses of manufacturing a multilayer printed circuit board of thepresent invention.

FIG. 17( a) to (c) are cross-section figures showing a part of processesof manufacturing a multilayer printed circuit board of the presentinvention.

FIGS. 18( a) to (c) are cross-section figures showing a part ofprocesses of manufacturing a multilayer printed circuit board of thepresent invention.

FIGS. 19( a) to (d) are cross-section figures showing a part ofprocesses of manufacturing a multilayer printed circuit board of thepresent invention.

FIGS. 20( a) to (d) are cross-section figures showing a part ofprocesses of manufacturing a multilayer printed circuit board of thepresent invention.

FIGS. 21( a) to (d) are cross-section figures showing a part ofprocesses of manufacturing a multilayer printed circuit board of thepresent invention.

FIGS. 22( a) to (c) are cross-section figures showing a part ofprocesses of manufacturing a multilayer printed circuit board of thepresent invention.

FIGS. 23( a) to (c) are cross-section figures showing a part ofprocesses of manufacturing a multilayer printed circuit board of thepresent invention.

FIG. 24 is a microscopic picture showing the cross-section of a via-holeof a multilayer printed circuit board of the present invention.

FIG. 25 is a microscopic picture showing the cross-section of a via-holeof a conventional multilayer printed circuit board.

Description of symbols  1 a substrate  2a, 2b a resin complex  2 a resininsulating layer  4 an under-level conductor circuit  4a a roughenedsurface  5 an upper layer conductor circuit  6 an opening part ofvia-hole  7 a via-hole  8 a copper foil  9 a plated-through hole  9a aroughened surface 10 a resin filler 11 a roughened layer 12 a Ni-Cualloy layer 13 an electroplating layer 14 a solder resist layer 15 anickel plating film 16 a gold plating film 17 a solder bump

DETAILED DESCRIPTION OF THE INVENTION

At first, an electroplating solution of the present invention will bedescribed below.

An electroplating solution of the present invention is an electroplatingsolution to be employed for manufacturing a multilayer printed circuitboard composed of a substrate bearing a conductor circuit and, asserially layered thereon, a resin insulating layer and a conductorcircuit in an alternate fashion and in repetition, characterized bycontaining 50 to 300 g/L of copper sulfate, 30 to 200 g/L of sulfuricacid, 25 to 90 mg/L of chlorine ion, and 1 to 1000 mg/L of an additivecontaining at least a levelling agent and a brightener.

An electroplating solution of the present invention makes it possible toperfectly fill an opening part of a via-hole and to form a via-hole(hereinafter such a via-hole may be referred as to a filled via) whoseupper face and the upper face of a conductor circuit in the same layerare in approximately the same plane in the case where a multilayerprinted circuit board is manufactured using the electroplating solution.That is, an electroplating solution of the present invention is optimumfor an electroplating solution for a filled via.

The foregoing electroplating solution contains 50 to 300 g/L of coppersulfate, 30 to 200 g/L of sulfuric acid, 25 to 90 mg/L of chlorine ion,and 1 to 1000 mg/L of an additive comprising at least a levelling agentand a brightener.

In the foregoing electroplating solution, if the concentration of coppersulfate is less than 50 g/L, no filled via can be formed and if itexceeds 300 g/L, the dispersion of the plating film thickness becomeswide.

Further, if the concentration of sulfuric acid is less than 30 g/L, theresistance of the solution increases and electroplating becomes hard totake place and if it exceeds 200 g/L, copper sulfate is easilycrystallized.

Further, if the concentration of chlorine ion is less than 25 mg/L, thegloss of a plating film is lowered and if it exceeds 90 mg/L, an anodeis hardly dissolved.

By using an electroplating solution with such a composition, a filledvia can be formed regardless of the opening diameter of the via-hole,the material and the thickness of a resin insulating layer andregardless of execution of the surface roughening of the resininsulating layer.

Further, if the foregoing electroplating solution is used in the case ofmanufacturing a multilayer printed circuit board, since theelectroplating solution contains a high concentration of copper ion,copper ion can sufficiently be supplied to an opening part for avia-hole and the opening part of for a via-hole can be plated at 40 to100 μm/hr plating speed, thus the speed of the electroplating processcan be increased.

Further, since the foregoing electroplating solution contains sulfuricacid in a high concentration, the resistance of the solution can belowered. The current density is, therefore, increased and the growth ofthe plating film in an opening part for a via-hole is not inhibited andthus the electroplating solution is suitable for formation of a filledvia structure.

The desirable composition of the foregoing electroplating solution is acomposition containing 100 to 250 g/L of copper sulfate, 50 to 150 g/Lof sulfuric acid, 30 to 70 mg/L of chlorine ion, and 1 to 600 mg/L of anadditive containing at least a levelling agent and a brightener.

The foregoing additive is sufficient if it contains at least a levellingagent and a brightener and may contain other components.

At least one substance selected from the group consisting ofpolyethylene, its derivatives, gelatin, and its derivatives, forexample, is preferable to be used as the foregoing levelling agent.

The foregoing polyethylene derivatives are not specifically limited andexamples of them are polyethylene isophthalate, polyethylene imine,poly(ethylene oxide), polyethylene glycol, polyethylene glycol ester,polyethylene glycol ether, polyethylene sulfide, polyether and the like.

Among them, polyethylene glycol or gelatin is desirable to be used. Thatis because they are widely usable and do not damage a resin insulatinglayer and a metal film.

Further, as the foregoing brightener, for example, at least one compoundselected from the group consisting of sulfur oxide, compounds related tosulfur oxide, hydrogen sulfide, compounds related to hydrogen sulfide,and other sulfur compounds is preferable to be used.

The foregoing sulfur oxide and compounds related to the sulfur oxide arenot specifically limited, and examples of them are sulfonic acid typecompounds, sulfone type compounds, sulfurous acid type compounds, andother sulfur oxide compounds.

The foregoing sulfonic acid compounds are not specifically limited, andexamples of them are sulfobenzoic acid, sulfobenzoate,sulfoanthraquinone, sulfomethane, sulfoethane, sulfocarbamide,sulfosuccinic acid, sulfosuccinic acid ester, sulfoacetic acid,sulfosalicylic acid, sulfocyanuric acid, sulfocyanogen, sulfocyanic acidester, sulfonine, sulfovinic acid, sulfophthalic acid, sulfonic acidamide, sulfonic acid imide and the like, and a sulfocarbonyl typecompound such as sulfocarboanilide and the like.

The foregoing sulfone compounds are not specifically limited, andexamples of them are sulfonal, sulfonyldiacetic acid,sulfonyldiphenylmethane, sulfoxylic acid, sulfoxylates, sulfonamide,sulfonimide, sulfonyl chloride type compounds and the like.

The foregoing sulfurous acid type compounds are not specificallylimited, and examples of them are sulfurous acid, ammonium sulfite,potassium sulfite, diethyl sulfite, dimethyl sulfite, sodium hydrogensulfite, sulfurous acid ester compounds and the like.

The foregoing other sulfur oxide compounds are not specifically limited,and sulfoxide and the like are examples.

The foregoing hydrogen sulfide and its related compounds are notspecifically limited, and examples of them are sulfonium compounds,sulfonium salts and the like.

The foregoing other sulfur compounds are not specifically limited, andbis-disulfide and the like are examples.

An electroplating solution of the present invention is capable ofcompletely filling an opening part of a via-hole with a metal by furthercontaining the foregoing brightener therein and forming the upper faceof a via-hole and the upper face of a conductor circuit of the samelayer in approximately the same plane by containing the foregoinglevelling agent therein in the case of manufacturing multilayer printedcircuit board.

That is because the foregoing brightener accelerates platingprecipitation on the opening part for a via-hole by activating the lowcurrent part of the opening part for a via-hole and also because theforegoing levelling agent suppresses the plating precipitation on thesurface of the conductor circuit by being adsorbed on the surface of theconductor circuit.

The addition amount of the foregoing levelling agent is preferably 1 to1000 mg/L and the addition amount of the foregoing brightener ispreferably 0.1 to 100 mg/L. The addition ratio of both is preferably(2:1) to (10:1).

If the addition amount of the foregoing levelling agent is too little,the amount of the levelling agent to be adsorbed on the surface of theconductor circuit is insufficient and it results in acceleration ofprecipitation on the conductor circuit. On the other hand, if the amountof the levelling agent is too much, the amount of the levelling agent tobe adsorbed on the bottom part of the opening part for a via-hole israther too much and it results in retardation of plating precipitationon the opening part for a via-hole.

Further, if the addition amount of the foregoing brightener is toolittle, the bottom of the opening part for a via-hole cannotsufficiently activated and therefore complete filling of the openingpart for a via-hole with metal cannot be carried out by plating. On theother hand, if the amount is too much, the plating precipitation in theconductor circuit part is accelerated and a step is formed between theupper face of the conductor circuit and the upper face of a via-hole.

An electroplating method using such an electroplating solution is notspecifically limited, and the following electroplating methods areapplicable.

That is, a general d.c. electroplating method (a DC plating method), amethod (a PC plating method) in which electric current is controlled tobe rectangular pulsed current by reciprocally repeating cathode currentsupply and interruption of the current supply, a pulse reverseelectroplating method (a PR plating method) in which electric current iscontrolled by periodically reversed waveforms by repeating reciprocalreverse of cathode current supply and anode current supply, and a methodin which high density electric current pulses and low density electriccurrent pulses are reciprocally applied as the cathode current.

Among these methods, the d.c. electroplating method is preferable from aviewpoint that the method is suitable for forming a filled via and thatthe method does not require a costly electric power source apparatus andcontrol apparatus in the case of manufacturing a multilayer printedcircuit board.

Next, a first method for manufacturing a multilayer printed circuitboard of the present invention will be described below.

The first method for manufacturing a multilayer printed circuit board ofthe present invention comprises at least the following processes (a) to(e):

(a) a process of forming a resin insulating layer having an opening partfor a via-hole by exposure and development treatment or laser treatment;

(b) a process of forming a metal layer comprising at least one elementselected from the group consisting of Cu, Ni, P, Pd, Co and W on thesurface of the resin insulating layer and the opening part for avia-hole;

(c) a process of forming a plating resist on the foregoing metal layer;

(d) a process of forming an electroplating film on a part un-coated withthe foregoing plating resist using an electroplating solution of thepresent invention; and

(e) a process of forming a conductor circuit by etching the metal layerexisting under the foregoing plating resist after the foregoing platingresist is separated.

Hereinafter, the first method for manufacturing a multilayer printedcircuit board of the present invention will be descried along the orderof the processes.

(1) In the first method for manufacturing a multilayer printed circuitboard of the present invention, at first a substrate comprising aninsulating substrate and a conductor circuit formed on the surface ofthe substrate is produced.

As the insulating substrate, a resin substrate is preferable andpractically, examples of the substrate are a glass-epoxy substrate, apolyimide substrate, a bismaleimide triazine resin substrate, a fluororesin substrate, a ceramic substrate, a copper-laminated laminate plateand the like.

In the method for manufacturing a multilayer printed circuit board ofthe present invention, a through hole is formed in such an insulatingsubstrate by a drill and the like and the wall face of the through holeand a copper foil surface are plated by electroless plating to form asurface conductive film and a plated-through hole. As the electrolessplating, a copper plating is preferable.

After the electroless plating, in general, the plated-through hole innerwall and the electroless plating film surface are subjected to surfaceroughening treatment. Methods applicable to the roughening treatmentare, for example, a blackening (oxidizing)-reducing treatment, sprayingtreatment with an aqueous mixed solution of an organic acid and a cupriccomplex and a treatment by Cu—NI—P acicular alloy plating and the like.

(2) Next, a conductor circuit is formed by forming an etching resist ina conductor circuit pattern on the substrate already plated byelectroless plating and etching the resultant substrate. After that, aresin filler is applied to the substrate surface bearing the conductorcircuit, dried to be a half-cured state and then polished to grind thelayer of the resin filler and the upper part of the conductor circuitand both main faces of the obtained substrate is leveled. After that,the layer of the resin filler is completely cured.

Incidentally, at the time of forming the layer of the resin filler, byusing a mask formed with an opening corresponding to the conductorcircuit non forming area, only the conductor circuit non forming areawhere is formed to be a recessed area by etching may be filled with theresin filler and then the foregoing polishing treatment is carried out.

(3) Next, a roughened layer or a roughened face (hereinafter referredalso as to a roughened layer) is formed on the conductor circuit basedon necessity. Methods as the roughening treatment method are, forexample, blackening (oxidizing)-reducing treatment, spraying treatmentwith an aqueous mixed solution of an organic acid and a cupric complexand a treatment by Cu—NI—P acicular alloy plating and the like.

(4) Next, based on necessity, a coating layer of tin, zinc, copper,nickel, cobalt, thallium, lead and the like is formed on the formedroughened surface by electroless plating or vapor deposition. That isbecause the conductor circuit exposed out from the resin insulatinglayer can be protected from a roughening solution and an etchingsolution by precipitating the foregoing coating layer in a thickness of0.01 to 2 μm. Hence tarnishment and dissolution of an inner layerpattern can reliably be prevented

(5) After that, an un-cured resin layer which is going to be a resininsulating layer by the following treatment is formed on the conductorcircuit on which the roughened layer is formed.

Applicable as a material of the foregoing resin insulating layer are athermosetting resin, a thermoplastic resin, a partially photosensitizedthermosetting resin, and composite resin thereof.

The foregoing un-cured resin layer may be formed by applying an un-curedresin or by thermally laminating an un-cured resin film. A resin film,which is an un-cured resin film bearing a metal layer of such as acopper foil in one face may be stuck on as well. In the case of usingsuch a resin film, the metal layer corresponding to a via-hole formationpart is etched and then an opening part is formed by radiating laserbeam. As the resin film bearing a metal layer, a copper-laminated resincan be used.

Among those materials of the resin insulating layer, a polyolefin typeresin, a polyphenylene type resin (PPE, PPO and the like), and a fluororesin are preferable since they are suitable for forming a resininsulating layer with a low dielectric constant.

Examples of the foregoing polyolefin resin are above mentionedpolyethylene, polypropylene, polyisobutylene, polybutadiene,polyisoprene, 2-norbornane, 5-ethylidene-2-norbornane, and copolymers ofthese resins and examples of the foregoing fluoro resin areethyl/tetrafluoroethylene copolymer resin (ETFE),poly(chlorotrifluoroethylene) (PCTFE) and the like.

Further, also applicable as a material of the foregoing resin insulatinglayer is a composite resin of the foregoing thermosetting resin and athermoplastic resin.

Examples of the foregoing thermoplastic resin are polysulfone (PSF),polyether sulfone (PES), polyphenylene sulfone (PPS), polyphenylenesulfide (PPES), polyphenylene ether (PPE), polyether imide (PI), aphenoxy resin, a fluoro resin and the like.

Among them, preferable ones are polysulfone (PSF), polyether sulfone(PES), polyether imide (PI), and/or a phenoxy resin. That is becausethey are particularly suitable to form a resin insulating layerexcellent in cracking resistance, shape retaining property owing to highheat resistance, excellent insulating property and high toughness value.

Examples of the foregoing thermosetting resin are an epoxy resin, aphenol resin, a polyimide resin and the like. Further, the foregoingthermosetting resin may be a photosensitized one and practically, thoseproduced by acrylation reaction of methacrylic acid or acrylic acid witha thermosetting group can be exemplified. Acrylated epoxy resins areparticularly preferable. Among them, an epoxy resin having 2 or moreepoxy groups in one molecule is especially desirable.

Examples of the foregoing epoxy resin are a cresol novolak type epoxyresin, a bisphenol A-type epoxy resin, a bisphenol F-type epoxy resin, aphenol novolak type epoxy resin, an alkylphenol novolak type epoxyresin, a biphenol F type epoxy resin, a naphthalene type epoxy resin, adicyclopentadiene type epoxy resin, an epoxylated condensate of a phenoland an aromatic aldehyde having a phenolic hydroxyl group, triglycidylisocyanurate, and an alicyclic epoxy resin. They may be used solely orin combination of two or more of them. Consequently, excellent heatresistance can be provided.

The mixing ratio of a thermoplastic resin and a thermosetting resin inthe foregoing resin composite is preferably 95/5 to 50/50=thethermosetting resin/the thermoplastic resin. That is because a hightoughness value can be retained without deteriorating the heatresistance.

Further, the foregoing resin composite may be a photosensitive resinprovided with photosensitivity. In the case where a photosensitive resinis used, an opening part for a via-hole can be formed by exposure anddevelopment treatment.

A concrete example of the foregoing resin composite is a resincomposition for roughened surface formation containing particles solublein an acid or an oxidizing agent (hereinafter, referred as to solubleparticles) being dispersed in a resin hardly soluble in an acid or anoxidizing agent (hereinafter, referred as to a hardly soluble resin) andthe like.

Incidentally, regarding the terms, hardly soluble and soluble, thosewith relatively high dissolution rates are to be called soluble andthose with relatively low dissolution rates are to be called hardlysoluble for the sake of convenience in the case where resins areimmersed in the same roughening solution for the same duration.

Examples of the foregoing soluble particle are a resin particle solublein an acid or an oxidizing agent (hereinafter referred as to a solubleresin particle), an inorganic particle soluble in an acid or anoxidizing agent (hereinafter, referred as to a soluble inorganicparticle), and a metal particle soluble in an acid or an oxidizing agent(hereinafter, referred as to a soluble metal particle). These solubleparticles may be used solely or in combination of two or more of them.

The shape of the foregoing soluble particle is not specifically limited,and may be spherical and crushed state. Addition to that, the shape ofthe foregoing soluble particle is preferably evenly shaped. That isbecause a roughened surface with uniform roughness can be formed.

The average particle size of the foregoing soluble particle ispreferably 0.1 to 10 μm. Two or more kinds of particles with differentparticle sizes may be used if their particle sizes are within the range.That is, a soluble particle with the average particle size of 0.1 to 0.5μm and a soluble particle with the average particle size of 1 to 3 μmmay be contained together. Consequently, further complicated roughenedface can be formed and a high adhesion strength to a conductor circuitcan be achieved. Incidentally, in this specification, the particle sizeof a soluble particle means the length of the longest part of thesoluble particle.

The foregoing soluble resin particle is not specifically limited unlessthe resin particle has a higher dissolution rate than that of theforegoing hardly soluble resin in the case where the particle isimmersed in an acid or an oxidizing agent and its concrete examples arean epoxy resin, a phenol resin, a polyimide resin, a polyphenyleneresin, a polyolefin resin, a fluoro resin, an amino resin (a melamineresin, an urea resin, a guanamine resin) and the like and may be usedsolely or a mixture of two or more of them.

Those preferable to be used as the soluble resin particle are (a) asoluble resin powder with the average particle size of 10 μm or smaller,(b) an agglomerated particle produced by agglomeration of a solubleresin powder with the average particle size of 2 μm or smaller, (c) amixture of a soluble resin powder with the average particle size of 2 to10 μm and a soluble resin powder with the average particle size of 2 μmor smaller, (d) a pseudo particle produced by stacking a soluble resinpowder and/or an inorganic powder, the average particle size of thoseare 2 μm or smaller, to the surface of a soluble resin powder with theaverage particle size of 2 to 10 μm, (e) a mixture of a soluble resinpowder with the average particle size of 0.1 to 0.8 μm and a solubleresin powder with the average particle size larger than 0.8 μm andsmaller than 2 μm, and (f) a soluble resin powder with the averageparticle size of 0.1 to 1.0 μm. Because they can form more complicatedanchors.

Further, as the soluble resin particle, a resin particle of rubber canbe used. Examples of the foregoing rubber is polybutadiene rubber,variously modified polybutadiene rubber such as an epoxy-modified one,an urethane-modified one, (meth)acrylonitrile-modified one and the like,and (meth)acrylonitrile-butadiene rubber containing carboxyl group. Byusing such rubber, the soluble resin particle is made easy to bedissolved in an acid or an oxidizing agent. In other words, in the caseof dissolving a soluble resin particle in an acid, the particle can bedissolved in an acid other than a strong acid and in the case ofdissolving a soluble resin particle in an oxidizing agent, the particlecan be dissolved even in permanganic acid with a relatively weakoxidative capability. Further in the case of dissolving in chromic acid,the dissolution can be carried out in a low concentration. For that,neither an acid nor an oxidizing agent remain on the surface of theresin and as it will be described somewhere later, so that such a casewhere no catalyst is provided or where a catalyst is oxidized at thetime when a catalyst such as a palladium chloride is supplied after theroughened surface formation can be avoided.

Examples of the foregoing soluble inorganic particles are particles ofone or more substances selected from the group consisting of an aluminumcompound, a calcium compound, a potassium compound, a magnesiumcompound, and a silicon compound.

Examples of the foregoing aluminum compound are alumina and aluminumhydroxide, examples of the foregoing calcium compound are calciumcarbonate, calcium hydroxide, an example of the foregoing potassiumcompound is potassium carbonate, examples of the foregoing magnesiumcompound are magnesia, dolomite, basic magnesium carbonate, and examplesof the foregoing silicon compound are silica and a zeolite. They may beused solely or in combination of two or more of them.

Examples of the foregoing soluble metal particle are particles of one ormore metals selected from the group consisting of copper, nickel, iron,zinc, lead, gold, silver, aluminum, magnesium, calcium, and silicon.Further, in order to keep insulating property, these soluble metalparticles may be coated with resin in the surface.

In the case of using two or more of these soluble particles are used asa mixture, the combination of the two types of soluble particles ispreferably a combination of a resin particle and an inorganic particle.That is because, owing to low conductivity of both, the insulatingproperty between upper and lower conductor circuits can reliably beretained and the thermal expansion in relation to an hardly solubleresin is easy to be controlled and no crack is formed in a resininsulating layer and no separation occurs between the resin insulatinglayer and the conductor circuit.

As the foregoing hardly soluble resin, those applicable are any resinwhich can maintain the roughened surface shape at the time of forming aroughened surface on a resin insulating layer using an acid or anoxidizing agent and a mixture of the foregoing thermoplastic resin andthe foregoing thermosetting resin may be used.

In the case where a resin composition for roughened surface formation isused for the foregoing resin composite, the foregoing soluble particleis preferable to be approximately evenly dispersed in the foregoinghardly soluble resin. That is because a roughened surface with uniformroughness can be formed and high adhesion to a conductor circuitincluding a via-hole can reliably be formed.

Further, a film containing a soluble particle may be used only for thesurface layer part to form a roughened surface thereon. In this case,since any parts except the surface layer part of the film are protectedfrom exposure to an acid or an oxidizing agent, the insulating propertyof conductor circuits having a resin insulating layer between them canreliably be maintained.

The mixing ratio by weight of the foregoing soluble particle ispreferably 5 to 50 wt. % to the solid content of the hardly solubleresin and further preferably 10 to 40 wt. %.

If the mixing weight ratio of the soluble resin is less than 5 wt. %. aroughened surface with the sufficient roughness cannot sometimes beformed and in the case of exceeding 50 wt. %, the insulating propertybetween upper and lower conductor circuits having a resin insulatinglayer between them cannot sufficiently be maintained and it sometimesresults in occurrence of short circuit since dissolution of the resininsulating layer reaches even in deeper part at the time of roughenedsurface formation by dissolving the soluble resin particle with an acidor an oxidizing agent.

The foregoing resin composition for roughened surface formation ispreferable to contain a hardening agent and other components other thanthe foregoing thermoplastic resin and the foregoing thermosetting resin.

Examples of the foregoing hardening agent are an imidazole typehardening agent, an amine type hardening agent, a guanidine typehardening agent, epoxy adducts of these hardening agents,microcapsulated ones of these hardening agents, and an organic phosphinetype compound such as triphenylphosphine, tetraphenylphosphoniumtetraphenyl borate, and the like.

The content of the foregoing hardening agent is preferably 0.05 to 10wt. % to a resin composition for roughened surface formation. If lessthan 0.05 wt. %, the resin composite is not sufficiently cured at thetime of forming a resin insulating layer and the degree of penetrationof a resin film with an acid becomes high at the time of forming aroughened surface on the resin insulating layer using an acid or anoxidizing agent and it sometimes results in deterioration of theinsulating property of the resin insulating layer. On the other hand, ifthe content exceeds 10 wt. %, the excess hardening agent componentsometimes denatures the resin composition, resulting in decrease of thereliability.

The foregoing other components include fillers of inorganic compoundsand resins which do not affect the formation of a roughened surface.

Examples of the inorganic compounds are silica, alumina, dolomite andthe like and examples of the resin are a polyimide resin, a polyacrylicresin, a polyamideimide resin, a polyphenylene resin, a melamine resin,an olefin type resin and the like. By adding such a filler, conformationof the thermal expansion coefficient and the heat resistance and thechemical resistance can be improved and the properties of a multilayerprinted circuit board can further be improved.

Further, the foregoing resin composition for roughened surface formationmay contain a solvent. Examples of the foregoing solvent are ketonessuch as acetone, methyl ethyl ketone, and cyclohexanone and aromatichydrocarbons such as ethyl acetate, butyl acetate, cellosolve acetate,toluene, xylene and the like. They may be used solely or in combinationof two or more of them.

By forming a resin insulating layer using the foregoing resin composite,a roughened surface can easily be formed on the resin insulating layerand further at the time when a plating layer is formed on the resininsulating layer bearing the roughened surface thereon by employing anelectroplating solution of the present invention, stress generated inthe plating layer is not so high and the stress is moderated, so that nocrack and no separation are caused in the resin insulating layer.Especially, preferable effects are obtained in the peripheral part of afilled via.

(6) Next, a resin insulating layer having an opening part for a via-holeis formed by exposure and development treatment or laser treatment.

The formation of the opening part of the via-hole is carried out usinglaser beam and oxygen plasma in the case where the resin matrix of theresin composite is a thermosetting resin, a polyolefin type resin, and acycloolefin type resin. In the case where the resin matrix is aphotosensitive resin, the formation is carried out by exposure anddevelopment treatment or laser treatment. The exposure and developmenttreatment is carried out before the hardening of a not-yet-curedphotosensitive resin layer. The foregoing laser treatment may be carriedout regardlessly before or after the thermal hardening or the photohardening.

Further, the exposure and development treatment is carried out byclosely setting a photomask (a glass substrate is preferable) drawing acircular pattern for opening part formation for a via-hole on aphotosensitive resin insulating layer in the state that the circularpattern side is kept on the resin layer side, exposing the resultantresin insulating layer, and either immersing the resin insulating layerin a development solution or spraying the solution to the resininsulating layer.

By hardening the uncured resin insulating layer formed on a conductorcircuit having a sufficiently roughened face, an resin insulating layerwith a high adhesion strength to the conductor circuit can be formed.

In the case of forming an opening part for a via-hole by using theforegoing laser beam, the laser beam to be employed is carbon dioxide(CO₂) laser, UV laser, excimer laser, YAG laser and the like. Amongthem, preferable are excimer laser and carbon dioxide gas laser in shortpulses.

This is because; the excimer laser, as described later, is capable offorming a large number of the opening part for the via-hole at one timeby using a mask formed with the through hole in the parts correspondingto the positions for forming the opening part for the via-hole and theshort pulsed carbon dioxide gas laser scarcely leaves resin residues inopening parts and slightly damages the resin in the peripheral parts ofopening parts.

Further, a hologram-method excimer laser as the excimer laser ispreferable to be employed. The hologram way means the a manner forradiating laser beam to an object matter through hologram, a condenser,a laser mask, a transfer lens and the like and by employing this manner,a large number of opening parts are efficiently formed one timeradiation.

In the case of employing carbon dioxide gas laser, the pulse intervalsare preferably 10⁻⁴ to 10⁻⁸ second. Further, the duration of the laserradiation for forming an opening part is preferably 10 to 500μ second.

In the case of employing excimer laser, the through hole of a maskformed with the a through hole in the part corresponding to the positionof the part to form the opening part for the via-hole are required to bein a true circular shape in order to make the spot shape of the laserbeam true circular, and the diameter of the foregoing through hole ispreferably around 0.1 to 2 mm.

In the case of forming an opening part by laser beam, especially byusing carbon dioxide gas laser, de-smearing treatment is preferably tobe carried out. The foregoing de-smearing treatment can be carried outusing an oxidizing agent of an aqueous solution of chromic acid or apermanganic acid salt. Further, the treatment may be carried out usingoxygen plasma, plasma of a mixture of CF₄ and oxygen, corona dischargeand the like. Further the surface may be modified by radiating UV raysusing a low pressure mercury lamp.

(7) Next, the surface roughening is carried out for a resin insulatinglayer on which an opening part for a via-hole is formed based on thenecessity. In the case a resin composition for roughened surfaceformation is used as a material for the resin insulating layer, theroughening treatment is, for example, carried out by dissolving andremoving a soluble resin particle existing on the surface of the resininsulating layer with an acid or an oxidizing agent.

The height of the roughened surface to be formed by acid treatment andthe like preferably satisfies the condition of Rmax=0.01 to 20 μm. Thatis in order to assure a high adhesion strength to a conductor circuit.Especially, in the case of a semi-additive method, the height ispreferably 0.1 to 5 μm. Because a metal layer can be removed whilekeeping high adhesion property.

In the case of carrying out such acid treatment, phosphoric acid,hydrochloric acid, sulfuric acid, or an organic acid such as formic acidand acetic acid may be used and especially an organic acid is preferableto be used because these hardly cause corrosion of a metal conductorlayer exposed out a via-hole in the case of forming a roughened surface.

The foregoing oxidation treatment, chromic acid and a permanganic acidsalt (potassium permanganate) is preferably used.

(8) Next, a thin metal layer of at least one element selected from thegroup consisting of Cu, Ni, P, Pd, Co and W is formed on the surface ofa resin insulating layer and an opening part for a via-hole.

The thickness of a metal layer is preferably 0.1 to 5 μM and furtherpreferably 0.5 to 2 μm. The foregoing metal layer is preferably formedby sputtering, plating, or in combination of sputtering with plating.

(9) Next, a plating resist is formed on the metal layer formed by theforegoing process (8).

As the foregoing plating resist, a photosensitive dry film and a liquidstate resist sold on the market may be used.

Further, the foregoing resist can be formed by sticking a photosensitivedry film or applying a liquid state resist and then carrying outexposure with UV rays and development with an aqueous alkaline solution.

(10) Next, using an electroplating solution of the present invention, anelectroplating film is formed on parts un-coated with the resist formedby the process (9). That is performed by immersing a substrate bearingthe foregoing metal layer and plating resist formed thereon in theforegoing electroplating solution. As a levelling agent to be containedto the foregoing electroplating solution, it is preferable to use one ormore substances selected from the group consisting of polyethylene, itsderivatives, gelatin and its derivatives and as the brightener to becontained to the foregoing electroplating solution, it is preferable touse one or more compounds selected from the group consisting of sulfuroxide, compounds related to it, hydrogen sulfide, compounds related toit, and other sulfur compounds.

As the electroplating, an electrolytic copper plating is preferable andthe thickness is preferable 3 to 25 μm in the conductor circuit partsexcept a via-hole. If the thickness is thinner than 3 μm, the upper faceof a via-hole and the upper face of a conductor circuit in the samelayer are sometimes not conformed to each other in approximately thesame plane, and if a conductor circuit with a thickness exceeding 25 μmis tried to be formed, the thickness of the plating resist is made thickand it sometimes occurs that the electroplating solution hardlypenetrates the parts where no plating resist is formed. The thickness isfurther preferably 5 to 15 μm. Further, the distance between the bottomface of a formed via-hole to the upper face is preferably 2 to 7 timesas long as the thickness of the foregoing conductor circuit part.

As a method for the foregoing electroplating is not specificallylimited, and as described above, a d.c. electroplating method ispreferable to be employed.

(11) Next, after the foregoing plating resist is parted by an aqueousstrongly alkaline solution and then the metal layer existing beneath isetched. Thus, an upper layer conductor circuit and a via-hole areindependently patterned.

Methods applicable to the foregoing etching may be chemical etchingusing an aqueous sulfuric acid/hydrogen peroxide solution, an aqueoussolution of ferric chloride, cupric chloride, and persulfates such asammonium persulfate and physical etching such as ion beam etching.

Palladium catalyst nuclei exposed in the parts other than conductorcircuit parts are removed by being dissolved by chromic acid, sulfuricacid, hydrogen peroxide and the like.

(12) If necessary, the processes (3) to (11) are repeated andelectroless plating or etching is carried out for a conductor circuit inthe uppermost layer in the same conditions as those of the foregoingprocess (3) to form a roughened layer or a roughened face on theconductor circuit in the uppermost layer.

Next, a solder resist layer is formed on the substrate surface includingthe conductor circuit in the uppermost layer. As the foregoing solderresist layer, examples are a polyphenylene ether resin, a polyolefinresin, a fluoro resin, a thermoplastic elastomer, a solder resist resincomposition and the like.

The foregoing solder resist layer is formed by applying an un-curedresin (a resin composition) by a roll coater method and then carryingout the above described opening treatment and the hardening treatment.

Examples of the foregoing solder resist resin composition are athermosetting resin containing a novolak type epoxy resin(meth)acrylate, an imidazole curing agent, bifunctional (meth)acrylicacid ester monomer, a polymer of (meth)acrylic aid ester with 500 to5000 molecular weight and bisphenol type ester resins, and a paste typefluid containing a photosensitive monomer of such as a polyvalentacrylic monomer and a glycol ether type solvent and the viscosity ispreferably adjusted to be 1 to 10 Pa·s at 25° C.

Examples of the foregoing novolak type epoxy resin (meth)acrylate areepoxy resins produced by reaction of acrylic acid or methacrylic acidwith glycidyl ether of phenol novolak or cresol novolak.

The foregoing bifunctional (meth)acrylic acid ester monomer is notspecifically limited, and esters of acrylic acid and methacrylic acidwith various kinds of diols are example.

After that, a solder bump is formed in the opening part in the foregoingsolder resist layer to complete the manufacturing processes of amultilayer printed circuit board of the present invention.

In addition to that, a letter printing process for formingproduct-identifying letters and oxygen or tetrachloromethane plasmatreatment may properly be carried out for the sake of modifying thesolder resist layer when necessary.

FIG. 1 is a cross-section figure of one cross-section of a multilayerprinted circuit board of the present invention and the first method formanufacturing the multilayer printed circuit board of the presentinvention is capable of manufacturing a printed circuit board in which,as being shown in FIG. 1, an opening part for a via-hole is completelyfilled with a metal and the upper face of a via-hole 7 and the upperface of a conductor circuit 4, 5 in the same layer are in approximatelythe same plane and further is capable of manufacturing a printed circuitboard having a stack via structure. Incidentally, the stack viastructure is a structure having a via-hole 7 and an another via-hole 7immediate above the via-hole 7 in an upper layer.

Next, a method for manufacturing a multilayer printed circuit boardaccording to the second method of the present invention will bedescribed.

The second method for manufacturing a multilayer printed circuit boardof the present invention comprises at least the following processes (a)to (d):

(a) a process of forming a resin insulating layer having an opening partfor a via-hole by exposure and development treatment or laser treatment;

(b) a process of forming a metal layer comprising at least one elementselected from the group consisting of Cu, Ni, P, Pd, Co and W on thesurface of the resin insulating layer and the opening part for avia-hole;

(c) a process of forming an electroplating film on the metal layer usingan electroplating solution of the present invention; and

(d) a process of forming a conductor circuit by etching after an etchingresist is formed on the foregoing electroplating film.

Hereinafter, the second method for manufacturing a multilayer printedcircuit board of the present invention will be descried along the orderof the processes.

Incidentally, the foregoing second method for manufacturing a multilayerprinted circuit board of the present invention only differs from theforegoing the first method for manufacturing a multilayer printedcircuit board of the present invention in the foregoing processes (c)and (d) and other than these processes (c) and (d), the same method asthe first method of the present invention for manufacturing a multilayerprinted circuit board may be employed to perform the method.Consequently, here, mainly the processes (c) and (d) of the foregoingsecond method for manufacturing a multilayer printed circuit board ofthe present invention will be described.

(1) At first, a thin metal layer is formed on the foregoing insulatinglayer and opening part of a via-hole in the same manner as those of theprocesses (1) to (8) of the method for manufacturing a multilayerprinted circuit board according to the first method of the presentinvention.

(2) Following that, using an electroplating solution of the presentinvention, an electroplating film is formed on the metal layer formed inthe process (1). It is performed by immersing a resultant substratebearing the foregoing metal layer formed thereon in the foregoingelectroplating solution. Additionally, as a levelling agent to becontained to the foregoing electroplating solution, at least onesubstance selected from the group consisting of polyethylene, itsderivatives, gelatin, and its derivatives is preferable to be used andas a brightener to be contained to the foregoing electroplatingsolution, at least one compound selected from the group consisting ofsulfur oxide, compounds related to sulfur oxide, hydrogen sulfide,compounds related to hydrogen sulfide, and other sulfur compounds ispreferable to be used.

As the electroplating, an electrolytic copper plating is preferable andthe thickness is preferably 3 to 25 μm in the conductor circuit partsexcept a via-hole. If the thickness is thinner than 3 μm, the upper faceof a via-hole and the upper face of a conductor circuit in the samelayer are sometimes not conformed to each other in approximately thesame plane and disconnection of a conductor circuit sometimes takesplace, and if the thickness exceeds 25 μm, an electroplating layer and ametal layer are sometimes not completely removed at the time of etching.The thickness is further preferably 5 to 15 μm. Also, the distancebetween the bottom face of a formed via-hole to the upper face ispreferably 2 to 7 times as long as the thickness of the foregoingconductor circuit part.

Although the foregoing electroplating method is not specificallylimited, as described above, a d.c. electroplating method is preferableto be employed.

(3) Further, after an etching resist is formed on the electroplatingfilm, etching is carried out to form a conductor circuit.

As the foregoing etching resist, a photosensitive dry film and a liquidstate resist sold on the market may be used.

Further, after a photosensitive dry film is stuck or a liquid stateresist is applied, exposure with UV rays and development with an aqueousalkaline solution are carried out.

(4) Next, a metal layer and an electroplating layer corresponding to theconductor circuit non forming area are removed by etching and then theetching resist is parted by an aqueous strong alkaline solution to formindependently patterned an upper layer conductor circuit and a via-hole.

Methods applicable to the foregoing etching may be chemical etchingusing an aqueous sulfuric acid/hydrogen peroxide solution, an aqueoussolution of ferric chloride, cupric chloride, and persulfates such asammonium persulfate and physical etching such as ion beam etching.

Palladium catalyst nuclei exposed in the parts other than conductorcircuit parts are removed by being dissolved by chromic acid, sulfuricacid, hydrogen peroxide and the like.

(5) Further, based on the necessity, as same in the method formanufacturing a multilayer printed circuit board according to the firstmethod of the present invention, processes from the process of forming aroughened layer on the conductor circuit surface to the process (theforegoing process (4)) of forming the conductor circuit are repeated andafter that, a roughened layer or a roughened face on the conductorcircuit is formed in the uppermost layer.

Next, as same in the first method for manufacturing a multilayer printedcircuit board of the present invention, a solder resist layer is formedand after that, a solder bump is formed in the opening part in theforegoing solder resist layer to complete the multilayer printed circuitboard manufacturing according to the second method for manufacturing amultilayer printed circuit board of the present invention.

Next, a multilayer printed circuit board of the present invention willbe described.

A multilayer printed circuit board of the present invention is amultilayer printed circuit board comprising a substrate bearing aconductor circuit and, as serially layered thereon, a resin insulatinglayer and a conductor circuit in an alternate fashion and in repetition,wherein the conductor circuits neighboring in up and down direction areconnected through a via-hole, characterized in that the foregoingvia-hole is filled with a metal, that the upper face of a via-hole andthe upper face of a conductor circuit in the same layer are keptapproximately in the same plane and that the distance from the bottomface to the upper face of the foregoing via-hole is about 2 to 7 timesas long as the thickness of the foregoing conductor circuit.

In a multilayer printed circuit board of the present invention, sincethe opening part for a via-hole is completely filled with a metal andthe upper face of the foregoing via-hole and the upper face of theforegoing conductor circuit in the same layer are approximately in thesame plane, no separation or no crack occurs between a conductor circuitincluding a via-hole and a resin insulating layer and also disconnectionof a conductor circuit in the upper layer of the conductor circuit doesnot take place. Further, the foregoing multilayer printed circuit boardcan be provided with a stack via structure with which the wiringdistance is shortened in order to provide a printed circuit board with ahigh speed and fine structure.

As a multilayer printed circuit board of the present invention, thosewith the structure illustrated in FIG. 1 are examples.

In a multilayer printed circuit board of the present invention, thedistance from the bottom face to the upper face of a via-hole is 2 to 7times as long as the thickness of the conductor circuit.

In the case of a printed circuit board comprising a conductor circuithaving the distance from the bottom face to the upper face of a via-holeexceeding 7 times as long as the thickness of the conductor circuit, theopening part for the via-hole is difficult to be completely filled witha metal and therefore the upper face of the via-hole and the upper faceof the conductor circuit in the same layer cannot sometime beapproximately in the same plane to make it difficult to form a stack viastructure. On the other hand the shallower the depth of an opening partof a via-hole is, the easier the filled via structure is formed, howeverin the case of a printed circuit board comprising a conductor circuithaving the distance from the bottom face to the upper face of thevia-hole less than 2 times as long as the thickness of the conductorcircuit, the upper face of the via-hole sometimes becomes higher thanthe upper face of the conductor circuit and disconnection of theconductor circuit sometimes takes place.

A resin insulating layer of the foregoing multilayer printed circuitboard is preferable to have a dielectric constant of 3.0 or lower at 1GHz.

By using a resin insulating layer with a dielectric constant of 3.0 orlower, delay and errors related to the electron signals can be preventedeven in the case the multilayer printed circuit board is used in a highfrequency band of 1 GHz or higher.

Resins to be used for the foregoing resin insulating layer may be thesame resins as those used in the first or the second method formanufacturing a multilayer printed circuit board of the presentinvention.

Such a multilayer printed circuit board of the present invention ispreferable to be manufactured by the first or second method formanufacturing a multilayer printed circuit board of the presentinvention.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in detail alongwith examples.

EXAMPLE 1

A. Preparation of a Resin Composite (an Adhesive for an Upper Layer)

(i) A mixture composition was produced by blending 35 parts by weight ofa resin solution produced by dissolving 80 wt. % of a cresol novolaktype epoxy resin acrylated in 25% (made by Nippon Kayaku Co., Ltd.:molecular weight 2,500) in diethylene glycol dimethyl ether (DMDG), 3.15parts by weight of a photosensitive monomer (made by Toagosei ChemicalIndustry Co., Ltd.: Aronix M 315), 0.5 parts by weight of a defoamingagent (made by San Nopco Ltd.: S-65), and 3.6 parts by weight ofN-methylpyrrolidone (NMP) in a container and mixing and stirring them.

(ii) Another mixture composition was produced by blending 12 parts byweight of polyether sulfone (PES), 7.2 parts by weight of an epoxy resinparticle (made by Sanyo Chemical Industries, Ltd.: Polymerpol) with theaverage particle size of 1.0 μm and 3.09 parts by weight of the particlewith the average particle size of 0.5 μm in another container and mixingand stirring the mixture and then further adding 30 parts by weight ofNMP and mixing and stirring the resultant mixture by a bead mill.

(iii) A mixture composition was produced by blending 2 parts by weightof an imidazole curing agent (made by Shikoku Chemicals Corp.:2E4MZ-CN), 2 parts by weight of a photopolymerization initiator (made byChiba Speciality Chemicals Corp.: Irgacure I-907), 0.2 parts by weightof a photosensitizer (made by Nippon Kayaku Co., Ltd.: DETX-S) and 1.5parts by weight of NMP in further another container and mixing andstirring the mixture.

A resin composite was produced by mixing the mixture compositionsproduced as (i), (ii) and (iii).

B. Preparation of a resin composite (an adhesive for an underlayer)

(i) A mixture composition was produced by blending 35 parts by weight ofa resin solution produced by dissolving 80 wt. % of a cresol novolaktype epoxy resin acrylated in 25% (made by Nippon Kayaku Co., Ltd.:molecular weight 2,500) in diethylene glycol dimethyl ether (DMDG), 4parts by weight of a photosensitive monomer (made by Toagosei ChemicalIndustry Co., Ltd.: Aronix M 315), 0.5 parts by weight of a defoamingagent (made by San Nopco Ltd.: S-65), and 3.6 parts by weight ofN-methylpyrrolidone (NMP) in a container and mixing and stirring them.

(ii) Another mixture composition was produced by blending 12 parts byweight of polyether sulfone (PES) and 14.49 parts by weight of an epoxyresin particle (made by Sanyo Chemical Industries, Ltd.: Polymerpol)with the average particle size of 0.5 in another container, mixing andstirring the mixture, and then further adding 30 parts by weight of NMPand mixing and stirring the resultant mixture by a bead mill.

(iii) A mixture composition was produced by blending 2 parts by weightof an imidazole curing agent (made by Shikoku Chemicals Corp.: 2E4MZ-CN,2 parts by weight of a photopolymerization initiator (made by ChibaSpeciality Chemicals Corp.: Irgacure I-907), 0.2 parts by weight of aphotosensitizer (made by Nippon Kayaku Co., Ltd.: DETX-S) and 1.5 partsby weight of NMP in further another container and mixing and stirringthe mixture.

A resin composite was produced by mixing the mixture compositionsproduced as (i), (ii) and (iii).

C. Preparation of a Resin Filler

(i) A resin filler with the viscosity of 40 to 50 Pa·s at 23±1° C. wasproduced by blending 100 parts by weight of a bisphenol F type epoxymonomer (made by Yuka Shell Epoxy Co.: molecular weight 310: YL 983U),170 parts by weight of a SiO₂ spherical particle (made by Admatechs Co.,Ltd.: CRS 1101-CE) coated with a silane coupling agent on the surfaceand having the average particle size of 1.6 μm and the diameter of themaximum particle of 15 μm or smaller and 1.5 parts by weight of alevelling agent (made by San Nopco Ltd.: Perenol S4) in a container andmixing and stirring the mixture.

Incidentally, 6.5 parts by weight of an imidazole curing agent (made byShikoku Chemicals Corp.: 2E4MZ-CN) was used as a curing agent.

D. A Method for Manufacturing a Printed Circuit Board

(1) A copper-laminated laminate plate composed of a substrate 1 which ismade of a 1 mm-thick glass epoxy resin or BT (bismaleimide triazine)resin with a 18 μm-thick copper foil 8 laminated on both sides of thesubstrate 1 was used as a starting material (reference to FIG. 2( a)).At first, the copper-laminated laminate plate was drilled to form athrough hole, subjected to electroless plating treatment and thenetching treatment in a pattern to form an under-level conductor circuit4 in both sides of the substrate 1 and a plated-through hole 9.

(2) After the resultant substrate in which the plated-through hole 9 andthe under-level conductor circuits 4 are formed was washed with waterand dried, the substrate was blackened in a blackening bath (anoxidizing bath) containing an aqueous solution containing NaOH (10 g/L),NaClO₂ (40 g/L) and Na₃PO₄ (6 g/L) and reduced in a reducing bathcontaining NaOH (10 g/L) an NaBH₄ (6 g/L) to form roughened faces 4 a, 9a in the entire surfaces of the under-level conductor circuits 4including the plated-through hole 9 (reference to FIG. 2( b)).

(3) After the resin filler described in the foregoing C was produced, alayer of the resin filler 10 was formed, by a method described below, inthe inside of the plated-through hole 9 and the parts where no conductorcircuit was formed on one side of the substrate 1 and the outerperipheries of the conductor circuits 4 within 24 hours after thepreparation.

That is, after the resin filler was squeezed in the plated-through holeby a squeegee, the filler was dried at 100° C. for 20 minutes. Then, amask drawing openings in parts corresponding to the conductor circuitnon forming area was put on a substrate and a layer of the resin filler10 was formed in the recessed parts which is the conductor circuit nonforming area by using a squeegee and dried at 100° C. for 20 minutes(reference to FIG. 2( c)).

(4) One side of the resultant substrate already subjected to the abovedescribed treatment (3) was subjected to polishing to polish the layerof the resin filler 10 formed in the outer peripheries of the conductorcircuits and the upper part of the resin filler 10 formed in theconductor circuit non forming area by a belt sander polishing using #600belt polishing paper (made by Sankyo Chemical Engineering Co.) and thensubjected to buffing to remove the scars formed by the foregoing beltsander polishing. A series of such polishing steps were carried out forthe other side in the same manner.

Incidentally, if necessary, etching might be carried out before andafter the polishing to level a land 9 a of the though hole 9 and theroughened faces 4 a formed in the under-level conductor circuits 4.

After that, heating treatment at 100° C. for 1 hour and successively at150° C. for 1 hour was carried out to completely harden the layer of theresin filler.

In such a way, the surface layer part of the resin filler 10 formed inthe plated-through hole 9 and in the conductor circuit non forming areaand the surfaces of the under-level conductor circuits 4 were leveled toobtain an insulating substrate where the resin filler 10 and the sidefaces 4 a of the under-level conductor circuits 4 were firmly stuck toeach other through the roughened faces and the inner wall face 9 of theplated-through hole 9 and the resin filler 10 were firmly stuck to eachother through the roughened faces (reference to FIG. 2( d)). That is,through the processes, the surface of the resin filler and the surfaceof an inner layer copper pattern would be in the same plane.

(5) After the foregoing substrate was washed with water and degreasedwith an acid, soft etching was carried out. And then, the surfaces ofthe under-level conductor circuits 4 and the land surface of theplated-through hole 9 were etched by spraying an etching solution toboth sides by sprays and then transported by transporting rolls to formroughened faces 4 a, 9 a with the thickness of 3 μm in the entiresurfaces of the under-level conductor circuits 4 (reference to FIG. 3(a)). A solution used as the etching solution was an etching solution(Made by Meck Co.: Mek Etch Bond) containing 10 parts by weight of animidazole-Cu(II) complex, 7 parts by weight of glycolic acid and 5 partsby weight of potassium chloride.

(6) To both sides of the substrate, the resin composite (viscosity: 1.5Pa·s) for an underlayer described in the foregoing description B wasapplied by a roll coater within 24 hours after its preparation and thenwas left for 20 minutes in horizontal state and dried (pre-baked) at 60°C. for 30 minutes. After that, the resin composite (viscosity: 7 Pa·s)for an upper layer described in the foregoing description A was appliedusing a roll coater within 24 hours after its preparation and then leftfor 20 minutes in horizontal state in the same manner and dried(pre-baked) at 60° C. for 30 minutes to form layers 2 a, 2 b of theresin composites with thickness of 35 μm (reference FIG. 3( b)).

(7) After a photomask film printed with black circles with the diameterof 85 μm was closely stuck to both sides of the resultant substrate onwhich the layers of resin composites were formed as described in (6) thesubstrate was exposed to light of 500 mJ/cm² intensity by an ultra highpressure mercury lamp and then subjected to spray development with aDMDG solution. After that, further the obtained substrate was exposed tolight of 3000 mJ/cm² intensity by an ultra high pressure mercury lamp,heated at 100° C. for 1 hour, at 120° C. for 1 hour, and at 150° C. for3 hours to form a resin insulating layer with the thickness of 35 μm andhaving opening parts 6 for via-holes with the diameter of 85 μm and ahigh size precision corresponding to the circle of the photomask film(reference FIG. 3( c)). Incidentally, in the opening part to be avia-hole, the roughened face of an under-level conductor circuit 4 wasexposed.

(8) The obtained substrate formed with the opening parts 6 for via-holeswas immersed in an aqueous chromic acid solution (7500 g/L) for 19minutes to dissolve and remove the epoxy resin particle existing on thesurface of the resin insulating layer and roughen the surface to obtaina roughened face. After that, the substrate was immersed in aneutralization solution (made by a Shiplay Co., Inc.) and washed withwater (reference FIG. 3( d)).

Further, a palladium catalyst (made by Atotech Co.) was supplied to thesurface of the substrate treated by the surface roughening treatment tostick the catalyst nuclei to the surface of the insulating layer and tothe inner wall face of the opening part for a via-hole.

(9) Next, the substrate was immersed in an aqueous electroless copperplating solution of the following composition to form an electrolesscopper plating film 12 with the thickness of 0.6 to 1.2 μm on the entireroughened surface (reference FIG. 4( a)):

[the aqueous electroless plating solution]

CuSO₄—5H₂O 10 g/L HCHO 8 g/L NaOH 8 g/L Rochelle salt 45 g/L an additive30 ml/L[the electroless plating conditions]at 35° C. solution temperature for 25 minutes.

(10) Next, electroplating on the entire surface of the electrolesscopper plating film was carried in the following conditions to form anelectroplating film 13 with the thickness of 7.5 μm (reference to FIG.4( b)):

[the aqueous electroplating solution]

CuSO₄—5H₂O 210 g/L sulfuric acid 150 g/L Cl⁻ 40 mg/L polyethylene glycol300 mg/L bisdisulfide 100 mg/L[the electroplating conditions]

current density 1.0 A/dm² duration 35 minutes temperature 25° C.

(11) A photosensitive dry film sold on the market was stuck to theelectrolytic copper plating film 13, a mask was put thereon, exposurewas carried out at 100 mJ/cm², and development treatment was carried outwith an aqueous solution of 0.8% sodium carbonate to form an etchingresist 3 with the thickness of 15 μm (reference FIG. 4( c)).

(12) Further, the parts other than the conductor circuits were etched byspray etching using an aqueous sulfuric acid/hydrogen peroxide solution.Successively, the resist film was separated and removed in an aqueoussolution of 40 g/L NaOH at 50° C. After that, the resultant substratewas subjected to heating treatment at 150° C. for 1 hour to form aconductor circuit with the thickness of 15 μm, which is composed of themetal layer and the electrolytic copper plating film and a filled via(reference FIG. 4( d)).

(13) To the substrate on which the conductor circuit was formed, thesame treatment as described in the process (5) was carried out to form aroughened face on the surface of the conductor circuit including thefilled via (reference 5(a)).

(14) Successively, the foregoing processes (6) to (13) were repeated toform conductor circuits in further upper layers to obtain a multilayerprinted circuit board with 8 layers. Incidentally, in Figs., one with 6layers was illustrated to make the structure easily understandable(reference FIG. 5( b) to FIG. 6( d)).

(15) Next, a solder resist resin composition with the viscosity of 2.0Pa·s at 25° C. was obtained by blending 46.67 parts by weight ofphotosensitive oligomer (molecular weight: 4000) which was a cresolnovolak type epoxy resin (made by Nippon Kayaku Co., Ltd.) whose 50% ofepoxy group was acrylated and which was dissolved in 60 wt. %concentration in diethylene glycol methyl ether (DMDG), 15 parts byweight of a bisphenol A type epoxy resin (made by Yuka Shell Epoxy Co.:Epikote 1001) dissolved in 80 wt. % concentration in methyl ethylketone, 1.6 parts by weight of an imidazole curing agent (made byShikoku Chemicals Corp.: 2E4MZ-CN), 3 parts by weight of a polyvalentacrylic monomer, which is a photosensitive monomer, (made by NipponKayaku Co., Ltd.: R 604), 1.5 parts by weight of also a polyvalentacrylic monomer (made by Kyoei Chemical Co., Ltd.: DPE 6A), and 0.71parts by weight of a dispersion type defoaming agent (made by San NopcoLtd.: S-65) in a container and mixing and stirring the obtained mixtureand further adding 2.0 parts by weight of benzophenone (made by KantoChemical Co., Inc.) as a photopolymerization initiator to the obtainedmixture composition and 0.2 parts by weight of Michler's ketone (made byKanto Chemical Co., Inc.) as a photosensitizer.

Incidentally, the viscosity measurement was carried out using a rotorNo. 4 and a rotor No. 3 of a B type viscometer (made by TokyoInstruments, DVL-B type) in the case of 60 min⁻¹ (60 rpm) and 4.6 min⁻¹(6 rpm), respectively.

(16) Next, after the solder resist resin composition was produced asdescribed foregoing (15), the composition was applied to both sides ofthe multilayer wiring substrate in 20 μm thickness, dried at 70° C. for20 minutes and at 70° C. for 30 minutes, exposed to UV rays of 1000mJ/cm² intensity while being closely covered with a 5 mm-thick photomaskdrawing a pattern corresponding to the opening parts of the solderresist, then the development with a DMTG solution was carried out toform an opening with the diameter of 200 μm.

Further, the resultant solder resist layer was hardened by heating inconditions: at 80° C. for 1 hour, at 100° C. for 1 hour, at 120° C. for1 hour, and at 150° C. for 3 hours to form a solder resist layer 14 (aninsulating organic resin layer) with the thickness of 20 μm and havingopenings in a solder pad part (including a via-hole and its land part)with opening diameter of 200 μm.

(17) Next, the substrate bearing the solder resist layer (an insulatingorganic resin layer) 14 was immersed for 20 minutes in an electrolessnickel plating solution at pH 4.5 containing nickel chloride (2.3×10⁻¹mol/L), sodium hypophosphite (2.8×10⁻¹ mol/L), and sodium citrate(1.6×10⁻¹ mol/L) to form a nickel plating layer 15 in the opening partwith the thickness of 5 μm. Further, the resultant substrate wasimmersed for 7.5 minutes at 80° C. in an electroless plating solutioncontaining potassium cyanoaurate (7.6×10⁻³ mol/L), ammonium chloride(1.9×10⁻¹ mol/L), sodium citrate (1.2×10⁻¹ mol/L) and sodiumhypophosphite (1.7×10⁻¹ mol/L) to form a gold plating layer 15 on thenickel plating layer 15 with the thickness of 0.03 μm.

(18) After that, a solder paste was printed in the openings of thesolder resist layer 14 and subjected to reflow at 200° C. to form solderbumps 17 and to manufacture a multilayer printed circuit board havingsolder bumps 17 (reference to FIG. 7( a)).

EXAMPLE 2

A. A Method for Manufacturing a Printed Circuit Board

(1) A copper-laminated laminate plate composed of a substrate 1 which ismade of a 0.8 mm-thick glass epoxy resin or BT (bismaleimide triazine)resin with a 18 μm-thick copper foil 8 laminated on both sides of thesubstrate 1 was used as a starting material (reference to FIG. 8( a)).At first, the copper-laminated laminate plate was drilled to form athrough hole, subjected to electroless plating treatment and thenetching treatment in a pattern to form an under-level conductor circuit4 in both sides of the substrate 1 and a plated-through hole 9.

(2) After the resultant substrate in which the plated-through hole 9 andthe under-level conductor circuits 4 are formed was washed with waterand dried, the following etching solution was sprayed to both sides ofthe substrate to etch the under-level conductor circuits 4 and the landsurface and the inner wall of the plated-through hole 9 and formroughened surfaces 4 a, 9 a in the entire surface of the under-levelconductor circuits 4 including the plated-through hole 9 (reference FIG.8( b)). The solution used as the etching solution was produced by mixing10 parts by weight of an imidazole-Cu(II) complex, 7 parts by weight ofglycolic acid, 5 parts by weight of potassium chloride, and 78 parts byweight of ion exchanged water.

(3) Next, a resin filler mainly containing a polyolefin type resin wasapplied to both sides of the substrate using a printing apparatus tofill the space between the under-level conductor circuits 4 and fill theplated-through hole 9 and heated and dried (reference FIG. 8( c)). Thatis, through this process, the resin filler 10 filled the space betweenthe under-level conductor circuits 4 and the inside of theplated-through hole 9.

(4) One side of the resultant substrate already subjected to the abovedescribed treatment (3) was subjected to polishing to polish the layerof the resin filler 10 formed in the outer peripheries of the conductorcircuits and the upper part of the layer of the resin filler 10 formedin the conductor circuit non forming area by belt sander polishing using#600 belt polishing paper (made by Sankyo Chemical Engineering Co.) andthen subjected to buffing to remove the scars formed by the foregoingbelt sander polishing. A series of such polishing steps were carried outfor the other side in the same manner.

Incidentally, if necessary, etching might be carried out before andafter the polishing to level a land 9 a of the plated though hole 9 andthe roughened faces 4 a formed in the under-level conductor circuits 4.

After that, heating treatment at 100° C. for 1 hour and successively at150° C. for 1 hour was carried out to completely harden the layer of theresin filler.

In such a way, the surface layer part of the resin filler 10 formed inthe plated-through hole 9 and in the conductor circuit non forming areaand the surfaces of the under-level conductor circuits 4 were leveled toobtain an insulating substrate where the resin filler 10 and the sidefaces 4 a of the under-level conductor circuits 4 were firmly stuck toeach other through the roughened faces, and the inner wall face 9 of theplated-through hole 9 and the resin filler 10 were firmly stuck to eachother through the roughened faces (reference to FIG. 8( d)).

(5) After the foregoing substrate was washed with water and degreasedwith an acid, soft etching was carried out and then the surfaces of theunder-level conductor circuits 4 and the land surface of theplated-through hole 9 were etched by spraying an etching solution toboth sides by sprays and after that the substrate was transported bytransporting rolls to form roughened faces 4 a, 9 a with the thicknessof 3 μm in the entire surfaces of the under-level conductor circuits 4.An etching solution used was the same one used in the foregoing process(2).

(6) To both sides of the substrate, a thermosetting type polyolefin typeresin sheet with the thickness of 50 μm was vacuum-laminated at thepressure of 0.5 MPa (5 kgf/cm²) with the temperature being increasedfrom 50 to 150° C. to form a resin insulating layer of the polyolefintype resin in each side. The vacuum degree at the time of vacuum bondingwas controlled to be 1330 Pa (10 mmHg) (reference FIG. 9( a)).

(7) Opening parts 6 for via-holes with diameter of 80 μm were formed inboth sides of the substrate bearing the resin insulating layers bycarbon dioxide (CO₂) gas laser in the conditions of beam diameter of 5mm, in the top hat mode, pulse width of 50μ second, the mask's holediameter of 0.5 mm, and 3 shots (reference FIG. 9( b)). After that,de-smear treatment was carried out using oxygen plasma.

(8) Plasma treatment was carried out to the obtained substrate in whichthe opening parts 6 for via-holes were formed to roughen the surface ofthe resin insulating layers (reference FIG. 9( c)). At that time, argonwas used as an inert gas and the plasma treatment was carried out usingSV-4540 made by ULVAC Japan Co., Ltd. for 2 minutes in conditions ofelectric power of 200 W, the gas pressure of 0.6 Pa and the temperatureof 70° C.

(9) Next, sputtering a target of an alloy of Ni and Cu was carried outto the substrate, in which the surface layers of the resin insulatinglayers were roughened, using SV-4540 made by ULVAC Japan Co., Ltd. inthe conditions of the pressure of 0.6 Pa, the temperature of 80° C.,electric power of 200 W, and 5 minute to form a Ni—Cu alloy layer 12 oneach surface of resin insulating layer 2 (reference FIG. 9( d)). In thiscase, the thickness of the formed Ni—Cu alloy layer was 0.2 μm.

Further, the substrate was subjected to conditioning and catalyst supplytreatment was carried out for 5 minutes in an alkaline catalyst.

(10) Next, electroplating of the entire surface of the Ni—Cu alloy layer12 was carried out in the following conditions to form an electroplatingfilm 13 with the thickness of 5 μm (reference to FIG. 10( a)):

[the aqueous electroplating solution]

CuSO₄—5H₂O 140 g/L sulfuric acid 120 g/L Cl⁻ 50 mg/L gelatin 300 mg/Lsulfonic acid amide 100 mg/L[the electroplating conditions]

current density 0.8 A/dm² duration 30 minutes temperature 25° C.

(11) A photosensitive dry film sold on the market was stuck to theelectrolytic copper plating film 13, a mask was put thereon, exposurewas carried out at 100 mJ/cm², and development treatment was carried outwith an aqueous solution of 0.8% sodium carbonate to form an etchingresist 3 with the thickness of 20 μm (reference FIG. 10( b)).

(12) Further, the parts other than the conductor circuits were etched byspray etching using an aqueous sulfuric acid/hydrogen peroxide solution.Successively, the resist film was separated and removed in an aqueoussolution of 40 g/L NaOH at 50° C. After that, the resultant substratewas subjected to heating treatment at 150° C. for 1 hour to form aconductor circuit with the thickness of 15 μm, which is composed of themetal layer and the electrolytic copper plating film and a filled via 7.The height difference of the height of the upper face of the formedconductor circuit and the height of the upper face of the filled viafrom the resin substrate 1 was 1 μm or thinner and thus both upper facesare approximately in the same plane and no recessed part was formed inthe upper of the via-hole (reference FIG. 10( c)).

(13) Successively, the foregoing processes (7) to (13) were repeated toform conductor circuits in further upper layers and obtain a multilayerprinted circuit board with 8 layers. Incidentally, in Figs., one with 6layers was illustrated to make the structure easily understandable(reference FIG. 11( a) to FIG. 13( a)).

Additionally, etching was carried out to the conductor circuit in thesurface layer using the same etching solution used in the foregoingprocess (2) to roughen the surface.

(14) Next, a solder resist resin composition with the viscosity of 2.0Pa·s at 25° C. was obtained by blending 46.67 parts by weight ofphotosensitivity providing oligomer (molecular weight: 4000) which was acresol novolak type epoxy resin (made by Nippon Kayaku Co., Ltd.) whose50% of epoxy group was acrylated and which was dissolved in 60 wt. %concentration in diethylene glycol methyl ether (DMDG), 15 parts byweight of a bisphenol A type epoxy resin (made by Yuka Shell Epoxy Co.:Epikote 1001) dissolved in 80 wt. % concentration in methyl ethylketone, 1.6 parts by weight of an imidazole curing agent (made byShikoku Chemicals Corp.: 2E4MZ-CN), 3 parts by weight of a polyvalentacrylic monomer, a photosensitive monomer, (made by Nippon Kayaku Co.,Ltd.: R 604), 1.5 parts by weight of also a polyvalent acrylic monomer(made by Kyoei Chemical Co., Ltd.: DPE 6A), and 0.71 parts by weight ofa dispersion type defoaming agent (made by San Nopco Ltd.: S-65) in acontainer and mixing and stirring the obtained mixture and furtheradding 2.0 parts by weight of benzophenone (made by Kanto Chemical Co.,Inc.) as a photopolymerization initiator to the obtained mixturecomposition and 0.2 parts by weight of Michler's ketone (made by KantoChemical Co., Inc.) as a photosensitizer.

Incidentally, the viscosity measurement was carried out using a rotorNo. 4 and a rotor No. 3 of a B type viscometer (made by TokyoInstruments, DVL-B type) in the case of 60 min⁻¹ (60 rpm) and 4.6 min⁻¹(6 rpm), respectively.

(15) Next, after the solder resist resin composition was produced asdescribed above (14), the composition was applied to both sides of themultilayer wiring substrate in 20 μm thickness, dried at 70° C. for 20minutes and at 70° C. for 30 minutes, exposed to UV rays of 1000 mJ/cm²intensity while being closely covered with a 5 mm-thick photomaskdrawing a pattern corresponding to the opening part of the solder resistwas drawn, and developed with a DMTG solution to form an opening withthe diameter of 200 μm.

Further, the resultant solder resist layer was hardened by heating inconditions: at 80° C. for 1 hour, at 100° C. for 1 hour, at 120° C. for1 hour, and at 150° C. for 3 hours to form a 20 μm-thick solder resistlayer 14 (an insulating organic resin layer) having openings in solderpad parts (including a via-hole and its land part) with opening diameterof 200 μm.

(16) Next, the substrate bearing the solder resist layer (an insulatingorganic resin layer) 14 was immersed for 20 minutes in an electrolessnickel plating solution at pH 4.5 containing nickel chloride (2.3×10⁻¹mol/L), sodium hypophosphite (2.8×10⁻¹ mol/L), and sodium citrate(1.6×10⁻¹ mol/L) to form a nickel plating layer 15 in the opening partwith the thickness of 5 μm. Further, the resultant substrate wasimmersed for 7.5 minutes at 80° C. in an electroless plating solutioncontaining potassium cyanoaurate (7.6×10⁻³ mol/L), ammonium chloride(1.9×10⁻¹ mol/L), sodium citrate (1.2×10⁻¹ mol/L) and sodiumhypophosphite (1.7×10⁻¹ mol/L) to form a gold plating layer 15 on thenickel plating layer 15 with the thickness of 0.03 μm.

(17) After that, a solder paste was printed in the opening of the solderresist layer 14 and subjected to reflow at 200° C. to form solder bumps17 and to manufacture a multilayer printed circuit board having solderbumps 17 (reference to FIG. 13( b)).

EXAMPLE 3

A. A Method for Manufacturing a Printed Circuit Board

(1) In the same manner as the processes (1) to (8) of the example 1, asubstrate bearing conductor circuits 4 and resin insulating layers 2 wasproduced and after that, an electroless copper plating film 12 wasformed in the same manner as the process (9) of the example 1 (referenceFIG. 14( a) to FIG. 16( a)).

(2) A photosensitive dry film sold on the market was stuck to theelectrolytic copper plating film 12, a mask was put thereon, exposurewas carried out at 100 mJ/cm², and development treatment was carried outwith an aqueous solution of 0.8% sodium carbonate to form a platingresist 23 with the thickness of 15 μm (reference FIG. 16( b)).

(3) Next, electroplating of the parts where no plating resist 23 wasformed was carried in the following conditions to form an electroplatingfilm 13 with the thickness of 7.5 μm (reference to FIG. 15( c)):

[the aqueous electroplating solution]

CuSO₄—5H₂O 210 g/L sulfuric acid 150 g/L Cl⁻ 40 mg/L polyethylene glycol300 mg/L bisdisulfide 100 mg/L[the electroplating conditions]

current density 1.0 A/dm² duration 35 minutes temperature 25° C.

Successively, the resist was parted and removed in an aqueous solutionof 40 g/L NaOH at 50° C. After that, the resultant substrate wassubjected to heating treatment at 150° C. for 1 hour and treated with anetching solution of an aqueous solution of sulfuric acid and hydrogenperoxide to remove the metal in parts other than the conductor circuitand to form the 8 μm-thick conductor circuit composed of the metal layerand the electrolytic copper plating film and filled vias 7 (referenceFIG. 16( d)).

(4) After that, the same processes as the processes (13) to (18) of theexample 1 were carried out to manufacture a multilayer printed circuitboard having solder bumps 17 (reference to FIG. 17 to FIG. 18).

EXAMPLE 4

A. Preparation of a Film of a Resin Composite

A solution of a resin composite was obtained by heating and dissolving30 parts by weight of bisphenol A type epoxy resin (epoxy equivalent469: made by Yuka Shell Epoxy Co.: Epikote 1001), 40 parts by weight ofa cresol novolak type epoxy resin (epoxy equivalent 215; Dainippon Inkand Chemicals, Inc.: Epiclon N-673) and 30 parts by weight of a phenolnovolak resin having a triazine structure (phenolic hydroxyl equivalent120: made by Dainippon Ink and Chemicals, Inc.: Phenolite KA-7052) in 20parts by weight of ethyl diglycol acetate and 20 parts by weight ofsolvent naphtha and further adding 15 parts by weight ofepoxy-terminated polybutadiene rubber (made by Nagase Chemicals Ltd.:Denalex R-45 EPT), 1.5 parts by weight of a milled product of2-phenyl-4,5-bis(hydroxymethyl) imidazole, 2 parts by weight of finepowdered silica, and 0.5 parts by weight of silicon type defoamingagent.

The obtained solution of the resin composite was applied to a PET filmusing a roll coater as to adjust the thickness after drying to be 50 μmand then dried at 80 to 120° C. for 10 minutes to produce a film of theresin composite.

B. A Method for Manufacturing a Printed Circuit Board

(1) In the same manner as the processes (1) to (4) of the example 1, asubstrate bearing a layer of a resin filler 10 in the plated-throughholes 9 and the conductor circuit non forming area was produced andafter that, the surface of an under-level conductor circuit 4 and theland surface of the plated-through holes 9 were etched in the samemanner as the process (5) of the example 1 to form roughened surfaces 4a, 9 a with thickness of 3 μm on the entire surface of the under-levelconductor circuit 4 (reference FIG. 19( a) to FIG. 20( a)).

(2) The resin composite film described in the description A was stuck toboth sides of the foregoing substrate by the following method using avacuum laminator apparatus to form a resin composite film layer in eachside and then the film layer was thermally hardened to form a resininsulating layer 2 (reference FIG. 20( b)). That is, the lamination ofthe foregoing resin composite film was carried out in conditions ofvacuum degree of 75 Pa, the pressure of 0.4 MPa, the temperature at 80°C., and the pressure bonding duration of 60 seconds and the foregoingthermal hardening was carried out in conditions of 100° C. for 30minutes and 150° C. for 1 hours

(3) Next, opening parts 6 for via-holes with diameter of 60 μm wasformed in the resin insulating layer by CO₂ gas laser of 10.4 μmwavelength in the conditions of beam diameter of 4.0 mm, in the top hatmode, pulse width of 8.0μ second, the mask's hole diameter of 1.0 mm,and 2 shots (reference FIG. 20( c)). After that, de-smear treatment wascarried out using oxygen plasma. Incidentally, the roughened face of anunder-level conductor circuit 4 was exposed in the a opening part 6 fora via-hole.

(4) The substrate with the opening parts 6 for via-holes was immersed inan aqueous solution of chromic acid (7500 g/L) for 19 minutes todissolve and remove epoxy resin particles existing on the surface of theresin insulating layer and to roughen the surface of the resininsulating layer to obtain the roughened surface. After that, theresultant substrate was immersed in a neutralization solution (made by aShiplay Co., Inc.) and washed with water (reference FIG. 20( d)).

Further, a palladium catalyst (made by Atotech Co.) was supplied to thesurface of the substrate treated by the surface roughening to stick thecatalyst nuclei to the surface of the insulating layer and to the innerwall face of the opening part 6 for a via-hole.

(5) Next, the substrate was immersed in an aqueous electroless copperplating solution of the following composition to form an electrolesscopper plating film 12 with the thickness of 0.6 to 1.2 μm on the entireroughened surface (reference FIG. 21( a)):

[the aqueous electroless plating solution]

CuSO₄—5H₂O 10 g/L HCHO 8 g/L NaOH 8 g/L Rochelle salt 45 g/L an additive30 ml/L[the electroless plating conditions]at 35° C. solution temperature for 25 minutes.

(6) A photosensitive dry film sold on the market was stuck to theelectrolytic copper plating film 12, a mask was put thereon, exposurewas carried out at 100 mJ/cm², and development treatment was carried outwith an aqueous solution of 0.8% sodium carbonate to form a platingresist 23 with the thickness of 20 μm (reference FIG. 21( b)).

(7) Next, electroplating of the parts where no plating resist 23 wasformed was carried in the following conditions to form an electroplatingfilm 13 with the thickness of 15 μm (reference to FIG. 21( c)):

[the aqueous electroplating solution]

CuSO₄—5H₂O 210 g/L sulfuric acid 150 g/L Cl⁻ 40 mg/L polyethylene glycol300 mg/L bisdisulfide 100 mg/L[the electroplating conditions]

current density 1.0 A/dm² duration 60 minutes temperature 25° C.

Successively, the plating resist 23 was parted and removed in an aqueoussolution of 40 g/L NaOH at 50° C. After that, the resultant substratewas subjected to heating treatment at 150° C. for 1 hour and treatedwith an etching solution of an aqueous solution of sulfuricacid-hydrogen peroxide to remove the metal in parts other than theconductor circuit and to form the conductor circuit with the thicknessof 15 μm and composed of the metal layer and the electrolytic copperplating film and filled vias 7 (reference FIG. 21( d)).

(8) The same treatment as the foregoing process (1) was carried out forthe substrate on which the conductor circuit was formed to formroughened face on the surface of the conductor circuit containing thefilled via (reference FIG. 22( a)).

(9) Successively, the foregoing processes (2) to (8) were repeated toform-resin insulating layers and conductive circuits in further upperlayers and to obtain a multilayer printed circuit board (reference FIG.22( b) to FIG. 23( b)).

(10) After that, the same processes as the processes (15) to (18) of theexample 1 were carried out to manufacture a multilayer printed circuitboard having solder bumps 17 (reference to FIG. 23( c)).

EXAMPLE 5

A multilayer printed circuit board was manufactured in approximately thesame manner as the example 4 except that a film made of a resincomposite composed of an epoxy resin (a thermosetting resin) and aphenoxy resin (a thermoplastic resin) was used as the film made of theresin composite.

EXAMPLE 6

A multilayer printed circuit board was manufactured in approximately thesame manner as the example 1 except that 400 mg/L of gelatin and 150ml/L of bisdisulfide were used as the additives for the electroplatingsolution.

EXAMPLE 7

A multilayer printed circuit board was manufactured in approximately thesame manner as the example 2 except that 400 mg/L of gelatin and 150ml/L of bisdisulfide were used as the additives for the electroplatingsolution.

EXAMPLE 8

A multilayer printed circuit board was manufactured in approximately thesame manner as the example 3 except that 400 mg/L of gelatin and 150ml/L of bisdisulfide were used as the additives for the electroplatingsolution.

EXAMPLE 9

A multilayer printed circuit board was manufactured in approximately thesame manner as the example 1 except that 400 mg/L of polyethylene glycoland 150 ml/L of sulfonic acid amide were used as the additives for theelectroplating solution.

EXAMPLE 10

A multilayer printed circuit board was manufactured in approximately thesame manner as the example 2 except that 400 mg/L of polyethylene glycoland 150 ml/L of sulfonic acid amide were used as the additives for theelectroplating solution.

EXAMPLE 11

A multilayer printed circuit board was manufactured in approximately thesame manner as the example 3 except that 400 mg/L of polyethylene glycoland 150 ml/L of sulfonic acid amide were used as the additives for theelectroplating solution.

EXAMPLE 12

A multilayer printed circuit board was manufactured in approximately thesame manner as the example 5 except that 400 mg/L of gelatin and 150ml/L of bisdisulfide were used as the additives for the electroplatingsolution.

EXAMPLE 13

A multilayer printed circuit board was manufactured in approximately thesame manner as the example 5 except that 400 mg/L of polyethylene glycoland 150 ml/L of sulfonic acid amide were used as the additives for theelectroplating solution.

COMPARATIVE EXAMPLE 1

A. Preparation of a resin composite (an adhesive for an upper layer),preparation of a resin composite (an adhesive for a lower layer) andpreparation of a resin filler were carried out in the same manner asexample 1.

B. Method for manufacturing printed circuit board

(1) A layer of a resin composite with the thickness of 35 μm was formedin the same manner as described in processes (1) to (6) of the example 1except that a substrate made of a glass epoxy resin or BT (bismaleimidetriazine) resin with thickness of 0.6 mm (reference FIG. 2( a) to FIG.3( b)) is used.

(2) Next, a resin insulating layer with the thickness of 35 μm havingopening parts for via-holes with the diameter of 90 μm was formed in thesame manner as described in the process (7) of the example 1 except thata photomask film printed with black circles with the diameter of 90 μmwas closely applied to both sides of the substrate bearing the layer ofthe resin composite (reference FIG. 3( c)). Incidentally, a roughenedsurface of an under-level conductor circuit was exposed in the openingparts to be via-holes.

(3) Further, the substrate in which the opening parts for via-holes wasconditioned and subjected to catalyst adhesion in an alkaline catalystfor 5 minutes and then the substrate was activated and immersed in anaqueous electroless copper plating solution with the followingcomposition to form an electroless copper plating film with thethickness of 1.1 μm on the entire surface:

[aqueous electroless plating solution]

CuSO₄—5H₂O 10 g/L HCHO 8 g/L NaOH 8 g/L Rochelle salt 45 g/L an additive30 ml/L[the electroless plating conditions]at 34° C. solution temperature for 25 minutes.

(4) Next, electroplating of the entire surface of the electroless copperplating film was carried in the following conditions to form anelectroplating film 13 with the thickness of 11 μm:

[the aqueous electroplating solution]

CuSO₄—5H₂O 80 g/L sulfuric acid 180 g/L Cl⁻ 40 mg/L additive 0.5 ml/L[the electroplating conditions]

current density 1.0 A/dm² duration 50 minutes temperature 27° C.

(5) A photosensitive dry film sold on the market was stuck to theelectrolytic copper plating film, a mask was put thereon, exposure wascarried out at 100 mJ/cm², and development treatment was carried outwith an aqueous solution of 0.8% sodium carbonate to form an etchingresist with the thickness of 20 μm and L/S=20/10 μm.

(6) Further, the parts other than conductor circuits were etched byspray etching using an aqueous sulfuric acid/hydrogen peroxide solution.Successively, the resist film was separated and removed in an aqueoussolution of 40 g/L NaOH at 50° C. After that, the resultant substratewas subjected to heating treatment at 150° C. for 1 hour to form a 15μm-thick conductor circuit composed of the metal layer and theelectrolytic copper plating film and a filled via.

(7) The substrate in which the conductor circuit was formed wassubjected to the same process as described in the process (5) to formroughened face with the thickness of 2 μm on the surface of theconductor circuit including the filled via.

(8) Successively, the processes (the processes (1) to (7) of theexample 1) for forming a layer of the composite resin described in (1)were repeated to form further upper layer conductor circuits to obtain amultilayer printed circuit board with 8 layers.

(9) Next, in the same manner as the process (15) of the example 1, asolder resist resin composition was obtained.

Also, through the processes similar to the processes (16) to (18) of theexample 1, a multilayer printed circuit board having solder bumps wasmanufactured.

The multilayer printed circuit boards having solder bumps obtained bythe examples and the comparative examples were cut with a cutter andtheir cross-sections were observed by a microscope. In the case wherethe multilayer printed circuit boards having solder bumps according tothe examples were cut with a cutter and their cross-sections wereobserved by a microscope, the difference between the height of upperfaces of the conductor circuits and the height of the upper faces of thefilled via-holes from the resin substrates was 1 μm or shorter to makeit clear that both upper faces were to be approximately in the sameplane and no recessed part was found to be formed in the upper faces ofthe via-holes. On the other hand, in the case of the multilayer printedcircuit board according to the comparative example, the opening partsfor the via-holes was not completely filled with a metal and recessedparts were found to be formed in the via-hole upper face.

Further, the multilayer printed circuit boards according to the exampleshad a stack via structure and as a result of a continuity test, thecontinuity was confirmed even in the part of the stack via structure. Onthe other hand, the multilayer printed circuit board according to thecomparative example was found not to have continuity in the part of thestack via structure, as a result of a continuity test.

INDUSTRIAL APPLICABILITY

As described above regarding an electroplating solution of the presentinvention, an opening part for a via-hole can perfectly be filled with ametal and a via-hole can be formed with the upper face of the via-holeand the upper face of a conductor circuit in the same layer being keptapproximately in the same plane by manufacturing a multilayer printedcircuit board by using the electroplating solution.

Also, by the method for manufacturing a multilayer printed circuit boardaccording to the first or second method of the present invention, anopening part for a via-hole can perfectly be filled with a metal and avia-hole can be formed with the upper face of the via-hole and the upperface of a conductor circuit in the same layer being kept approximatelyin the same plane and a multilayer printed circuit board having a stackvia structure can be manufactured.

Further, in a multilayer printed circuit board of the present invention,since an opening part for a via-hole is perfectly filled with a metaland the upper face of the via-hole and the upper face of a conductorcircuit in the same layer are kept approximately in the same plane, noseparation and crack take place between a conductor circuit including avia-hole and a resin insulating layer and no disconnection of aconductor circuit in the upper layer of the former conductor circuitoccurs, resulting in improvement of the connection reliability.Moreover, the foregoing multilayer printed circuit board can have astack via structure with which the wiring distance is shortened in orderto satisfy the requirements of the high speed and fine property of aprinted circuit board.

1. A multilayer printed circuit board comprising a substrate; a firstconductor circuit formed on the substrate; a first resin insulatinglayer having an opening for a via-hole, the first resin insulating layerbeing formed on the substrate and the first conductor circuit; a secondconductor circuit formed on the first resin insulating layer; a via-holeconnecting the first conductor circuit and the second conductor circuit,the via-hole being a filled via; wherein the second conductor circuitcomprises an electroless plating film having a thickness which is from0.1 to 5 μm and an electroplating film having a thickness which is from3to 25 μm on the electroless plating film, the filled via comprises theelectroless plating film and the electroplating film filling theopening, an entire upper face of the filled via is substantially flat,the upper face of the filled via and an upper face of the secondconductor circuit are kept approximately in the same plane, and adistance from a bottom face to the upper face of the filled via is about2 to 7 times as long as the thickness of the second conductor circuit.2. The multilayer printed circuit board according to claim 1, whereinthe first resin insulating layer has a dielectric constant of 3.0 orlower at 1 GHz.
 3. The multilayer printed circuit board according toclaim 1 wherein a second resin insulating layer having an opening with avia-hole is formed on the second conductor circuit, the filled via andthe first resin insulating layer, the via-hole in the second resininsulating layer is disposed immediately over the via-hole in the firstresin insulating layer.
 4. The multilayer printed circuit boardaccording to claim 1, wherein a thickness of the electroplating film is5 to 15 μm.